Traditionally, bipolar batter assemblies, such as that taught in US Publication No. US 2009/0042099, incorporated herein by reference, include an electrolyte within a stack of electrode plates, located between the separators and electrode plates. The electrolyte allows electrons and ions to flow between the cathode and anode material of the electrode plates. To provide an electrode which does not leak from the electrode stack or into channels of the stack, a solid electrolyte can be used to reduce the need for separate sealing members within the battery assembly.
Although the use of solid electrolyte may be useful in preventing leakage of the electrolyte, it can be advantageous to fill a battery assembly with a liquid electrolyte under a vacuum. Pairs of electrode plates of the battery assembly may form electrochemical cells. By sealing off the battery assembly and filling under a vacuum, an electrolyte may be able to be drawn into the individual electrochemical cells. Under a vacuum, the electrolyte fill rates may be expedited to allow for commercially acceptable fill rates; air pockets or bubbles may be prevented from forming between layers of the battery assembly; and electrochemical cells may be uniformly filled with electrolyte. U.S. Pat. Nos. 4,861,686; 5,470,679; 5,682,671; EP Patent No. 0402265; and PCT Publication No. WO 1994/007272, incorporated herein by reference in their entirety for all purposes, discuss the advantages of filling battery assemblies under a vacuum. US Publication No. 2014/0349147, incorporated by reference in its entirety for all purposes, teaches an elegant solution for filling a battery assembly with a liquid electrolyte while using interlocking components to create a leak proof seal to prevent leaking of the liquid electrolyte. Notwithstanding the above, there is still a need to incorporate a liquid electrolyte into a battery assembly while eliminating the need for complex sealing configurations to prevent the electrolyte from leaking from or within the battery assembly.
To draw a vacuum from a battery assembly, the battery assembly may be placed within a vacuum chamber to activate drawing of an electrolyte into the cells of the battery. Alternatively or in conjunction with a vacuum chamber, separate openings in the battery assembly may be used for drawing the vacuum and filling the assembly with an electrolyte. The drawbacks associated with having separate ports for drawing a vacuum and filling a battery assembly include additional component and manufacturing costs for separate ports and increased time and difficulty to connect and seal multiple ports during assembly in mass production environments. US Publication No. 2014/0349147 teaches how to overcome the need for a separate vacuum chamber and use a single port as a vacuum purge port and an electrolyte fill port. Notwithstanding the above, there is still an ongoing need to quickly fill a battery assembly with electrolyte while ensuring adequate and uninform filling of each electrochemical cell.
Generally, battery assemblies include end plates designed to resist outward bulging during operation of a bipolar battery assembly to properly maintain a seal about and within the battery assembly. The outward bulging is a result of a positive pressure differential between the higher pressures experienced inside of the battery assembly during operation compared to the external pressure (i.e., atmospheric pressure). As taught in US Publication No. 2014/0349147, the use of heavy end plates can be avoided by using an internal structure within the battery assembly which creates an external seal and prevents any liquid or gas from escaping the battery assembly. It may be advantageous to avoid bulky or heavy end plates to provide for a lighter weight battery assembly so that the battery assembly may be integrated into a number of systems which take overall system weight into account. A problem encountered when a single port is used for both creating an internal vacuum within the battery assembly and filling the battery assembly, is internal forces are created when the interior of the battery assembly during creation of the vacuum.
When a single port is used both for creating an internal vacuum within the battery assembly and filling the battery assembly, internal forces are created within the interior of the battery assembly. These internal forces are a result of the negative pressure differential between the extremely low pressure within the interior of the battery assembly due to the vacuum. While a stack of electrode plates having a pair of end plates and/or interlocked electrode plates are sufficiently rigid to withstand outward deformation from positive pressure differentials during operation of a battery assembly, typical electrode plates and end plates may not be able to resist inward deformation from an internal vacuum. Inward deformation may be defined as an inward bending or collapsing of an electrode plate. Generally, as an end plate is attached only about at least a portion of periphery to an adjacent electrode plate, the end plate does not prevent inward deformation of adjacent electrode plate. This inward deformation of the electrode plate may result in reduced interior volume of the battery assembly prior to filling with electrolyte, causing non-uniform and inadequate filling of the electrolyte into the cell. Additionally, as disclosed in US 2014/0349147, stacks of electrode plates may be sealed about their edges and/or along the length of channels formed through the stack through an interference fit. The inward deformation of the electrode plates may result in breaking of the interference fit, thus breaking the seal and causing electrolyte to leak outside of the battery assembly and/or into one or more channels, and the deformed electrode plate may become cracked or otherwise permanently deformed.
What is needed is a battery assembly able to incorporate a liquid electrolyte into a battery assembly under an internal vacuum which maintains a seal about the liquid electrolyte. What is needed is a battery assembly having a single port for both pulling a vacuum inside of the battery assembly and uniformly filling the battery assembly with a liquid electrolyte. What is needed is a lighter weight battery assembly able to resist outward deformation of electrode plates resulting from temperatures and pressures generated during operation and inward deformation of the electrode plates resulting from the creation of an internal vacuum. What is needed is a low weight external support structure.